The present invention relates generally to bi-directional satellite communication systems and more particularly to systems and methods for selecting chains of forward link equipment that transmit signals to a mobile platform.
In bi-directional communications systems of the related art, a ground station transmits and receives signals to and from a satellite, and the satellite, in turn, transmits and receives signals to and from a mobile platform. Typically, a plurality of satellites are present that cover particular geographic regions, and each satellite further includes a plurality of transponders that receive data from the ground station and subsequently transmit data to the mobile platform. In addition, the mobile platform includes receive and transmit antennas, which are used to communicate with the satellite transponders.
A ground station typically includes equipment that transmits signals to the satellite transponders. Further, some ground stations include additional back-up equipment in the event of an original equipment failure. When the original equipment fails, the equipment can be manually repaired or replaced, or a switch can be made to the back-up equipment. Generally the switch is made when monitoring equipment recognizes a failure of the original equipment and directly switches to the back-up equipment. In many instances of equipment failure, signal transmission is interrupted for an extended period of time, which can severely threaten operation of the mobile platform, depending on the type of data being transmitted.
Accordingly, there remains a need in the art for a communications system that can quickly and efficiently switch between transmission equipment with minimal disruption in service to the mobile platform.
In one preferred form, the present invention provides a communications system and method that comprises a ground station having a route server in communication with a router, which further communicates with primary chains of forward link equipment. The term xe2x80x9cforward linkxe2x80x9d is used to denote transmissions from the ground station to a mobile platform, and the term xe2x80x9creturn linkxe2x80x9d is used to denote transmissions from the mobile platform to the ground station.
The primary chains of forward link equipment transmit signals to satellite transponders, which in turn transmit the signals to mobile platforms, e.g. aircraft. The signals generally comprise data that is requested by the mobile platform including, but not limited to, command and control, telemetry, unicast (Internet), and multicast (video, audio). In addition to the primary chains of forward link equipment, the present invention further comprises spare chains of forward link equipment that are employed when the primary chains of forward link equipment fail.
Generally, a forward link assignment manager is aware of all available equipment and assigns equipment to forward links. In addition, the route server contains all paths to all chains of forward link equipment, and the forward link assignment manager assigns a cost to each path according to the availability of the path. The lower the cost of the path, the more available the path. The route server then presents the paths, along with their costs, to the router, which always selects the lowest cost path for subsequent transmission of the signals to the transponders. If a primary chain of forward link equipment that has been selected by the router fails, the forward link assignment manager reassigns the forward link equipment and increases the path cost of the failed equipment to a level higher than that of the spare equipment paths such that the router will choose the path of a spare chain of forward link equipment. Once the router has selected a path for a spare chain of forward link equipment, the route server stops providing the path of the failed primary chain of forward link equipment to the router and the forward link assignment manager removes the failed path from the network topology.
Additionally, if the spare chain of forward link equipment also fails, the router will similarly select a path for an alternate spare chain of forward link equipment in accordance with the method as previously described. The router will further select paths for alternate spare chains of forward link equipment as the spare chains fail, until no spare chains of forward link equipment remain.
Preferably, the forward link assignment manager is informed of the failed chain of forward link equipment by the mobile platform. Accordingly, each path of both the primary and spare chains of forward link equipment are assigned a unique multicast signature message address, hereinafter referred to as a xe2x80x9cunique address.xe2x80x9d The unique address is transmitted to the mobile platform along with the data signals, via the transponders, such that the mobile platform is continuously aware of the path being used. The mobile platform, in turn, transmits the unique address to the forward link assignment manager, thereby informing the forward link assignment manager which chain is currently transmitting data. When a chain of forward link equipment fails, the unique address is no longer transmitted to the forward link assignment manager such that the forward link assignment manager recognizes that the chain has failed. The forward link assignment manager then increases the cost of the failed chain to a level higher than that of the spare chains, and the router accordingly selects a spare chain of forward link equipment.
When the spare chain of forward link equipment is operational, the mobile platform receives a different unique address, and accordingly transmits the unique address to the forward link assignment manager. As a result, the forward link assignment manager is made aware of the spare chain of forward link equipment being operational and thus removes the failed chain of forward link equipment from the network topology.
In another preferred form, the primary and spare chains of forward link equipment further comprise a built in test system that is capable of determining whether a failure has occurred. If a failure of a chain of forward link equipment occurs, the built in test system transmits signals to the forward link assignment manager informing the forward link assignment manager of the failure. The forward link assignment manager then increases the cost of the failed chain of forward link equipment so that the router will choose a lower cost chain of forward link equipment. Once the lower cost chain of forward link equipment is operational, the forward link assignment manager removes the failed chain of forward link equipment from the network topology.
In another preferred form, the present invention further comprises a monitoring system that monitors the forward link signal traffic from the chains of forward link equipment to the transponders. If a failure of a chain of forward link equipment occurs, the monitoring system informs the forward link assignment manager of the failure. Similarly, the forward link assignment manager then increases the cost of the failed chain of forward link equipment so that the router will choose a lower cost chain of forward link equipment. Again, once the lower cost chain of forward link equipment is operational, the forward link assignment manager removes the failed chain of forward link equipment from the network topology.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.